Magnetic device



June 10, 1930.,

E. D. MEAD MAGNETIC DEVICE)? Filed Aug. 15, 1929 s Sheets-Sheet 1WVE/W'O/P ED. MEAD 5v ATTORNEY June 10,1930. E. D. MEAD 2,731

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MAGNETIC DEVICE Filed Aug. 15. 1929 s Sheets-Shet a ATTORNEY PatentedJune 10, 1930 1 UNITED STATES PATENT OFFICE EDWARD D. MEAD, F CALDWELL,NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED, OFNEW YORK, N. Y., A CORPORATION OF NEW YORK MAGNETIC DEVICE Applicationfiled August 15, 1929. Serial No. 386,207.

This invention relates to magnetic devices and particularly toelectromagnetically operated devices for measuring telephone serv- Theobject of the invention is to secure an improved measuring instrumentwhich is efficient and dependable in operation and also one which isrugged and compact in construction.

Heretofore, various types of telephone substation meters have beenproposed for measuring the amount of use the subscriber makes of histelephone. Many of these are open to the objection that they are notefiieient enough to operate on the low operating currents available.Others are not dependable in that they respond to ringing cur rents andto transient currents that may appear in the line. Others are delicatein construction and subject to damage in handling and shipping.

According to the present invention, these objections are overcome bymeans of an instrument comprising a ponderous U-shaped permanent magnetsuspended on a metallic reed, thus obviating bearings and pivots whichoffer considerable friction and which are also easily damaged. Thepole-pieces of the permanent magnet cooperate magnet- 30 ically with thepoles of a stationary H-shaped electromagnet. Due to the shape of theelectromagnet, a large winding space is afforded for the coils, aconstant air-gap is provided for all positions of the instrument, thusavoiding undue bias, and a very efficient magnetic circuit is had sincea substantially complete reversal of flux is secured through the core ofthe windings as the permanent magnet oscillates.

A feature of the invention is a device in which the magnetic circuit isso designed that the polarizing flux tends to hold the rotor in itsextreme positions, when once placed in either of these positions; thisbiasing force is almost exclusively effective only in the end positionsand there is practically no tendency to move the rotor from intermediatepositions to either of these extreme positions. The actuating elementsare so disposed in the case that a relatively small current, through thewinding of the electromagnet, will be sufiicient to overcome this endbias.

The drawing comprising Figures 1 to 10 inclusive shows a telephonemetering device in which this invention is embodied.

Fig. 1 is a front View of the meter as it appears when installed forservice.

Fig. 2 shows the base plate and inner casing, the outside cover havingbeen removed.

Fig. 3 shows the innercover, which is partially cut away in Fig. 2.

Fig. 4 is a front view of the device with both the outer and innercovers removed.

Fig. 5 is a top view of the actuating elements only, and Fig. 6 is a topView of a horizontal section of the actuating elements taken at 6-6 inFig. 4, the indicating mechanism having been removed.

Fig. 7 is a rear view of the actuating elements and Fig.8 is a detaildrawing of the upper support for the metallic reed on which thepermanent magnet is suspended.

Figures 9 and 10 show an alternative arrangement of the actuatingelements of a metering device which is, in other respects, similar tothat shown in Figures 1 to 8 inclusive.

The meter shown in the drawing consists of a non-magnetic metallicframework of two members and (see Fig. 7), an electromagnet whose core39 is rigidly supported by the member 15, a permanent magnet 22 which issuspended by the reed 36 from a horizontally projecting arm of member 20and which is pivoted at the upper and lower extrenfities l6 and 17 ofthe member 15 to permit a limited angular movement, a gear train 66 andindicating mechanism (not shown in Fig. 4:) fastened to member 15 andarranged for actuation by the movement of the permanent magnet, a base 1and easing 5, an inside cover 11, and a1; outside cover 2. (See Figs. 1,2, 3 and 4.

The framework, by which the electromagnet, permanent magnet, andindicating mechanism are supported fits into the metal casing 5 (asshown in Fig. 4) and is fastened thereto by screws 18 and 19. The easing5 is aflixed to and extends out from the metal base 1, and the insidecover 11 which fits over the front of easing 5 is fastened to base 1 bystuds 1i and the nuts which are turned onto the threaded ends of thesestuds. The end of one of these studs projects yond the nut and a hole isdrilled in the projecting portion so that the assembled meter exclusiveof the outside cover may be sealed at the factory. The base, casing andinside cover constitute a magnetic shield for the actuating elements ofthe meter. The base 1 is arranged to be fastened to a wall or othervertical support, the screw holes 3 and l being provided therefor. Theoutside cover 2 tits over the casing onto base i being fastened by screw8 to the inner cover 11. "he base is formed so that either a glass or ametal outside cover may be used. A seal 10 passes through the head ofscrew 8 and the lug 9, which is aihxed to the cover, so as to preventtampering with the mechanism after installation. The opening 12 in cover11 and the glass 7 inserted in a corresponding opening in cover 2 maizethe dial plate (37 and indicators 68 visible from the front of themeter. The opening 6 in base 1 is used as an entrance for the wiresleading in from the circuit which controls the operation of the meter;the lead-in wires (not shown) are e:-:tended through the insulating tubeto lugs 51 on terninal blocl: 50 (see i). In the case of a telephonemeter installed at a subsc'i ers station, the line conductors from thecentral oiiice are connected to the outer pair of lugs and theconductors from the telephone i11 strunient are connected to the innerpair of hugs. These lugs are connected by conductors 4:8 and i9 (shownin Fig. 7) to the windings it and d5 of the electromagnet in such amanner that one of the windings is inserted in one side of the line andthe othe' winding is inserted in the other side of the line. Additionallugs are protided for the termination and extension of other conductorsassociated with the subscribers instrument. The opening 13 in cover 11gives access to the terminal block 50 by removing the outer cover only.

The magnetic metallic core 39 of the electromagnet is fastened by screws58 (shown in Fig. (3) to framework member 20. The core is ii-shaped, hecoils i l and L5 being wound around the middle member of the corebetween the non-magnetic spool heads &6 and The limbs 40 and ill at oneend of core 39 are adjacentto the pole piece 25 of the north pole ofpermanent magnet 22; and the limbs -1 and i3 at the other end of core 39are adjacent to the pole piece 26 of the south pole of permanent magnet22.

A portion of the frainew rk member extends horizontally outward to forma support from which the permanent magnet 22 is suspended. (See Figs. 7and 8). The upper end of reed 36 is fastened in a metal disc 35, thedisc being seated in the project ing portion 3d of the frame. A lever 58is set into disc and projects outward for use in adjusting the angularposition of the disc so to vary the torque of reed 36. Set screw 37 isprovided it: i the disc in the desired position. The lUV r end of reed36 passes through a slit in the upper side of a clamping device 23. Theclamp 23 fits over the bottom of the U-shaped permanent magnet, beingfastened thereto by screws 2%; the lower end of reed 36 is bent at rightangles so as to be held between the clamp and the magnet. The clamp 28is pivoted by a pin extending downward into the projecting portion 17 offramework member 15. To form an upper pivotior magnet 22, a metal yoke31 is fastened by screws 32 and clamping devices 27 and 2S, and byscrews 29 and 3 respectively shown in F ig. 7) to the 22; and a pinextends up surface of yoke 31 into the projecting 'tion 16 of frameworkmember 15. This arrangement permits the ma net 22 to move back and forthabout an 2 h the center 0 the pins whic portions 16 and 17 of frameiorkmember 15, the weight off the magnet being a ried by reed The adjustablecork faced stops 5% and (sec F 5 and 6) secured to framework member 20,and the spring buffers 56 and 57 fastened to the limbs of magnet 22,limit the movement of the magnet about this axis. The buffers and stopsalso prevent IGQOUECL when the magnet 22 reaches the end of its movem'tin either direction, without tending to retain the magnet in either oilits extreme positions when the electromagnet energized for moving the innet .2 into the other of its extreme positions. The screws 32 and 3 bywhich yoke 31 is fastened to clamping devices 27 and 28, also serve tosecure the pole pieces and 2G to the N and S poles, respectivel ofmagnet 22. The po'a pieces and the ends of the core are so shaped thatthe air gap, between the pole pieces and the adjacentlimbs of the core,stant when the magnet 22 is moved i-jrom one extreme position to theother. Each pole piece embraces an arc of such length that in either ofthe extreme PO, .lons of magnet 22 only one of the limbs at each end ofcore 39 is covered by th correspond pole piece. For instance, with themagnet 22 in one extreme position as shown in Fig. (5, pole piece coversthe end of limb d0 without covering the end of limb il; while pole piece26 covers the end at limb 4.3 without covering the end of limb 4-2.

The mechanism for driving the indicator train (see Figs. and incnudes apin which extends horizontally forward from the side ofyoke 31 to engagethe forked end ofdriving lever 60. Two driving pawls 61 and 62 arepivoted on extensions of lever so as to engage ratchet wheel 63. Themovement of the magnet 22 from one extreme position to the other is thuseffective to advance the ratchet wheel 63. The advance of wheel 63 is inturn transmitted through its spin dle to the first gear in thetrain 66.The ratchet wheel 63 and gears 66 are mounted between plates 64 and 65,the gear spindles extending frontward through the dial plate .67 whichis attached to the front of plate 64. The hands attached to the end ofthe ar spindles indicate on their respective ials the number ofreversals of current through the windings of the electromagnet by whichthe permanent magnet has been moved from one position to the other. Inthe case ofa telephone meter the hands indicate the number ofconversation units for which the subscriber, at whose station the meteris installed, is to be charged. The indicating mechanism is fastened tovframework member 20 by screws 69.

With the ermanent magnet 22 in its midposition and with no currentthrough the windings of the electromagnet there is no force tending torotate magnet 22, but when the magnet 22 is in either of its extremepositions there is a force tending to hold it in this position; this endbiasing force renders the reed 36 ineffective to return magnet 22 to itsmid-position when the actuating current through the windings of theelectromagnet ceases. The position of the magnetic elements (withrespect to the base, casing and inside cover) and the amplitude of theangular movement of the permanent magnet, as controlled by stops 54 and55, are such that the operating current, which is 're uired to overcomet-hisbiasing force, is no arger than necessary. When the magnet 22 is inthe position shown in Fig. 6, the circuit for the major portion of theporalizing flux, which produces the biasing force, may be traced fromthe N pole of magnet 22, through pole piece 25, through the air gap tolimb 40 of core 39, through the middle of core 39, through limb 43,across the air gap and throughpole piece 26, to the S pole of magnet 22,and throughthe magnet back to theN pole; if the'magnet 22 is in theother of its extreme positions the circuit for the polarizing fluxincludes the limbs 41 and 42 of core 39 instead of limbs 40 and 43.

When the windings 44 and 45 are energized by a current of suflicientmagnitude and duration in one direction the fields of the permanent'andelectromagnets react to move magnet 22 to one of its extreme positions;and when the current is in the opposite direction magnet 22 is moved tothe other of its extreme positions. In the case of a telephone meter,successive reversals of current over the line (every 1 5 seconds, orother desired interval) rotate the magnet back and forth, from one endposition to the other, during the time that the calling and calledsubscribers stations are connected for talking.

In the alternative arrangement, shown in Figs. 9 and 10, the permanentmagnet is rigidly fastened to the framework and the electromagnet ismovable to actuate the indicating mechanism. Fig. 9 is a front View andFig. 10 shows a vertical section at 1010 as indicated in Fig. 9.

The limbs of the permanent magnet 72 extend through holes in theframework member 71 and are clamped thereto in the desired position bythe bar 73 and screws 74. The projecting portions 84 and 91 (see Fig.10) form the bearings on which the electromagnet can rotate back andforth within its extreme positions. tion 84 extends into the detail 82Whichis fastened by screws 83 to the extending portions of spool heads78 and 79; and the pin 85 projects upward from the bottom of detail 82into the projection 84 so as to pivot the electromagnet at that point.The lower bearing is a ball thrust bearing whose seat 92 is screwed intothe projection 91; the position of ball 93 may be adjusted therein byturning screw 98. The pin 94 whose lower surface rests on the ball 93extends downward from detail 95 which is fastened by screws 96 to thespool heads 78 and 79; thus the weight of the movable .member is carriedby the ball hearing so that friction is reduced to a minimum. The metalbar 99 which is held by screws 96 and 97 between the lower portions ofspool heads 78 and 79 adds mass to the movable member so as to renderthe meter less susceptible to momentary impulses of current and tomechanical vibration. The lead-in wires 100 are carried through the tube89 into detail 88, which is fastened by the clamping device 90 to themiddle portion of the permanent magnet, and then downward along the axisof rotation through insulating strips 86 (which are fastened to detail82 by screws 87) to the windings 81 of the electromagnet. Thisarrangement eliminates any torsional resistance, in the lead-in wires,to the movement of the electromagnet.

The coil 81 of the electromagnet is Wound around the middle member ofthe H-shaped core 80 between the spool heads 78 and 79. The core 80extends between pole pieces 75 and 76 which are screwed, respectively,to the N and S poles of magnet 72. The pole pieces and core are shapedto maintain a uniform air gap; and the pole pieces are of such a lengththat each covers only one of the core' ends when the electromagnet is ineither of its extreme positions, the cir- The projec-.

cuits for the polarizing flux being similar to those hereinbeforedescribed for the preferred embodiment of this invention.

The indicating mechanism, base, and covers for the alternativearrangement are not shown but may be similar to those disclosed in Figs.1, 2 and 3. i

The scope of the invention, which is not limited to the specificembodiments herein disclosed, is indicated by the claims.

lVhat is claimed is:

1. In combination, a U-shaped permanent magnet suspended to oscillatefreely from one position to another, a stationary electromagnet locatedbetween the pole-pieces of said permanent magnet having oppositepole-pieces presented respectively to the opposite pole-pieces of saidpermanent magnet such that the air gaps between the electromagnet andsaid permanent magnet are constant for different positions of thepermanent magnet, an energizing coil for said electromagnet, and meansactuated in response to the oscillation of said permanent magnet.

2. In combination, a U-shaped permanent magnetsuspended to oscillatefreely from one position to another, an H-shaped electromagnet locatedbetween the pole-pieces of said permanent magnet having its oppositepole-pieces presented respectively to the opposite pole-pieces of saidpermanent magnetsuch that the air gaps between the electromagnet and thepermanent magnet are uniform for all positions of the permanent magnet,an energizing coil wound on said H-shaped magnet, and means actuated inresponse to the oscillation of said permanent magnet.

3. In combination, a permanent magnet suspended on a reed foroscillation from one position to another, a stationary electromagnetlocated between the pole-pieces of said permanent magnet and havingopposite pole-pieces presented respectively to the opposite pole-piecesof said permanent magnet, an energizing coil for said electromagnet, anda driven element actuated in response to the oscillation of saidpermanent magnet.

I. In combination, a J-shaped permanent magnet, an electromagnet havingan H- shaped core, a framework supporting both of said magnets in such amanner that one end of each pole of said electromagnet is adjacent tothe N pole of said permanent magnet and the other end of each pole ofsaid electromagnet is adjacent to the S pole of said permanent magnet,one of said magnets being supported by said framework in such a mannerthat it can rotate from one extreme position to another, and meansactuated by the movement of said suspended magnet.

5. In combination, a U-shaped permanent magnet, an electromagnet havingan H- shaped core located between the pole pieces of said permanentmagnet so that one end of each pole of said electromagnet is adjacent tothe N pole of said permanent magnet and the other end of each pole ofsaid electromagnet is adjacent to the S pole of said electromagnet, anda framework supporting both of said magnets in such amanner that one ofsaid magnets can be rotated from one extreme position to another withoutvarying the air gap between the core of said electromagnet and the polepieces of said permanent magnet.

6. I11 combination, a U-shaped permanent magnet, an electromagnet havingan H- shaped cor located between the pole pieces of said permanentmagnet so that one end of each pole of said electromagnet is adjacent tothe N pole of said permanent magnet and the other end of each pole ofsaid electromagnet is adjacent to the S pole of said electromagnet, aframework supporting both of said magnets in such a manner that one ofthem is free to rotate from one position to another without varying theair gap between the adjacent portions of said core and said pole pieces,the energization of the coil of said electromagnet by current in onedirection being eifective to rotate said one of said magnets to one ofits extreme positions, the energization of the coil of saidelectromagnet by current in the opposite direction being effective torotate said one of said magnets to the other of its extreme positions,and means actuated by the movement of said one of said magnets.

7. A magnetic device comprising a permanent magnet, an electromagnethaving a core extending between the poles of said permanent magnet sothat one end of each pole of said electromagnet is adjacent to the Npole of said permanent magnet and the other end of each pole of saidelectromagnet is adjacent to the S pole of said permanent magnet, aframework for rigidly supporting one of said magnets and for suspendingthe other of said magnets so that the suspended mag net can rotate fromone extreme position to another, and means actuated by the movement ofsaid suspended magnet.

8. In a magnetic device, an electromagnet having an H-shaped core, apermanent magnet, a frame supporting said magnets so that one of saidmagnets is free to rotate from one position to another, and a circuitfor the flux of said permanent magnet which includes one leg of eachpole of said electromagnet for holding said rotatable magnet in one ofits extreme positions without appreciably tending to cause saidrotatable magnet to rotate from an intermediate position to said extremeposition.

9. In a magnetic device, a permanent magnet, an electromagnet having anH-shaped core, one of said magnets being free to rotate from one extremeposition to another, a circuit for the flux of said permanent magnetwhich includes one leg of each pole of said electromagnet for holdingsaid rotatable magnet in one of its extreme positions with outappreciably tending to cause said rotatable magnet to move from anintermediate position to said extreme position, and means actuated bythe movement of said rotatable magnet.

10. In a magnetic device, a U-shaped permanent magnet suspended torotate freely from one position to another, a vstationary electromagnethaving an H shaped core, a coil for said electromagnet wound around themiddle member of said core, a circuit for the flux of said permanentmagnet which includes one leg of each pole of said electromagnet forholding said permanent magnet in one of its extreme positions withoutappreciably tending to cause said permanent magnet to move from anintermediate position to said extreme position, and means actuated bythe movement of said permanent magnet.

11. In combination, two magnets one of which is a permanent magnet andthe other an electromagnet, pole pieces for said permanent magnet, anH-shaped core for said electromagnet, a frame rigidly supporting one ofsaid magnets, means including said frame for supporting the other ofsaid magnets in such a manner that it can rotate back and forth betweentwo limiting positions, a coil for said electromagnet wound around themiddle member of said core so that its energization by current in onedirection causes the rotation of said rotatable magnet to one of itslimiting positions and its energization by current in the otherdirection causes the rotation of said rotatable magnet to the other ofits limiting positions, and means actuated by the movement of saidrotatable magnet.

12. A magnetic device comprising a U- shaped permanent magnet, polepieces for said permanent magnet, an electromagnet having an H-shapedcore located between said pole pieces, a frame for rigidly supportingsaid electromagnet, means for suspending said permanent magnet from saidframe so that said permanent magnet can rotate on a vertical axiswithout varying the air gap between said core and said pole pieces,means for limiting the rotation of said permanent magnet between twopositions in each of which one of said pole pieces overlaps thecorresponding end of one pole of said electromagnet and said coilwithout overlapping the corresponding end of the other pole of saidelectromagnet and the other of said pole pieces overlaps thecorresponding end of said other pole of said electromagnet and said coilwithout overlapping the corresponding end of said one pole of saidelectromagnet, and means actuated by the movement of said permanentmagnet.

13. In combination, a U-shaped permanent magnet, an electromagnet havingan H- shaped core located between the poles of said permanent magnet, aframe rigidly supporting said electromagnet, means including said frameand a metallic reed for suspending and pivoting said permanent magnet insuch a manner that it can rotate, stop pins for limiting the rotation ofsaid permanent magnet in either direction, means for preventin reboundof said ermanent magnet when it reaches either of its limitingpositions, a coil for said electromagnet wound around the middle memberof said core so that its energization by current in one direction causessaid permanent magnet to rotate to one of its limiting positions and itsenergization by current in the other direction causes said permanentmagnet to rotate to the other of its limiting positions, pole pieces forsaid permanent magnet so proportioned that in either of the limitingpositions of said permanent magnet one of said pole pieces overlaps theadjacent end of one pole of said electromagnet and said coil withoutoverlapping the adjacent end of the other pole of said electromagnet,and means actuated by the movement of said permanent magnet.

In witness whereof, I hereunto subscribe my name this 9th day of August,1929.

EDWARD D. MEAD.

